The present invention relates to an apparatus and a method for use in pumping fluids in a wellbore, wherein the apparatus and method are for use with a downhole rotary pump. Further, the present invention relates to an apparatus and a method wherein a pipe string defining an interior fluid path for the passage of the fluids therein is used to actuate the downhole rotary pump.
To produce downhole production fluids from a wellbore to the surface, conventional production systems typically include a tubing string extending from a wellhead at the surface through the wellbore to the hydrocarbon producing formation. The downhole end of the tubing string is connected with a downhole pump which typically pumps the production fluids from the formation and to the surface through the tubing string. Further, the pump is actuated by a rotating or reciprocating rod string which extends within the tubing string from the wellhead at the surface to the downhole pump. Similar systems are provided for injecting fluids from the surface downhole through the wellbore to the formation.
For instance, in a conventional downhole rotary pump, commonly referred to as a progressive cavity pump, the rod string is rotated within the tubing string by a motor associated with the wellhead at the surface. Rotation of the rod string actuates a rotor within the downhole pump in order to produce the downhole production fluids to the surface. More particularly, the production fluids are pumped to the surface within the tubing string in the annular space formed between the rod string and the tubing string.
Alternately, in a downhole pump including a reciprocating plunger for pumping the production fluids, the rod string is reciprocated within the tubing string by a walking beam or other pump drive system associated with the wellhead at the surface which vertically lifts or reciprocates the rod string. Reciprocation of the rod string actuates the reciprocating plunger within the downhole pump to produce the downhole production fluids to the surface.
However, actuation of the downhole pump by the rotation or reciprocation of the rod string within the tubing string has not been found to be fully satisfactory for various reasons. For instance, it has been found that the rod string tends to be prone to structural failure. Structural failure of the rod string is particularly prevalent where the rod string is subjected to an amount of torque in order to rotate the rod string and thereby rotate the rotor within the downhole pump.
Further, where a rotating rod string is used to actuate the downhole pump, it has been found that the rod string may not be able to provide a required or desired amount of torque to the rotor of the pump to optimize the operation or functioning of the downhole pump. In other words, the downhole pump may not be able to be used efficiently or to its maximum capacity due to the limitations inherent in the structure of the rod string and the potential for its failure.
As well, the rotation of the rod string to actuate the pump tends to cause wearing of the tubing string and rod string failure as a result of abrasion between the rod string and the inner surface of the tubing string. For instance, the rod string may include a plurality of rods interconnected by rod couplings and may be connected to the downhole rotary pump by a further coupling referred to as a shear coupling located just above the rotary pump. The rod couplings and the shear coupling are larger in diameter than the rods comprising the rod string.
As a result, wearing occurs along the length of the rod string but tends to be greatest at the locations where the rod couplings and the shear coupling contact the inner surface of the tubing string. Wearing of the inner surface of the tubing string can result in a hole developing in the tubing string and a possible loss of production fluids due to leakage. Further, where high concentrations of silt and sand are produced from the wellbore along with the production fluids, the abrasive nature of the silt and sand accelerates the wearing that occurs between the rod string and the inner surface of the tubing. In addition, the wearing is further accelerated when the wellbore being produced is slant, directionally or horizontally drilled.
Various attempts have been made to address these issues by eliminating the need for or the use of the rod string. However, none of these attempts have been fully satisfactory, particularly when using a downhole rotary pump or a progressive cavity pump to produce the production fluids from the formation.
For instance, attempts have been made to eliminate the use of a reciprocating rod string to actuate a downhole reciprocating pump. United States of America U.S. Pat. No. 4,661,052 issued Apr. 28, 1987 to Ruhle describes a downhole reciprocating pump including a pump plunger, which is activated by the axial oscillation or reciprocation of a string of lightweight composite pipe. The string of pipe is axially oscillated from the surface. More particularly, the string of pipe is provided to activate the reciprocating pump by axially oscillating the pump plunger and to transport the production fluids to the surface.
United States of America U.S. Pat. No. 5,351,752 issued Oct. 4, 1994 to Wood et. al. also describes a downhole reciprocating pump including a reciprocating pump plunger. Specifically, a tubing string is connected between a pump drive at the surface, referred to as a jack unit, and the downhole reciprocating pump. The tubing string performs the dual function of reciprocating the pump plunger in response to activation of the pump drive at the surface and transporting production fluids from the formation to the surface.
Further, attempts have been made to eliminate the use of a rotating rod string to actuate a downhole pump. United States of America U.S. Pat. No. 5,220,962 issued Jun. 22, 1993 to Muller et. al. describes the use of a rotating tubing string to activate a particular downhole pump. Specifically, the downhole pump is comprised of a first section, a second section and a third section. The first section of the downhole pump is connected to the downhole end of the tubing string and rotates circumferentially in response to the rotation of the tubing string. The second section of the downhole pump is connected to the first section and reciprocates longitudinally in response to the rotation of the first section. The third section is connected to the second section and receives the production fluids from the wellbore and subsequently pushes the fluids uphole in response to the longitudinal reciprocation of the second section.
United States of America U.S. Pat. No. 5,667,369 issued Sep. 16, 1997 to Cholet describes the use of a continuous tube or continuous length of coil tubing in place of the rod string to activate the downhole rotary pump. Specifically, a tubular column extends from the surface for connection to the downhole rotary pump. The tubular column is described as a xe2x80x9cproduction columnxe2x80x9d which has as its main role the channeling of the production fluids from the bottom of the wellbore to the surface xe2x80x9cvia its inner pipexe2x80x9d. The coil tubing extends from the surface through the production column for connection to a rotor of the downhole rotary pump. Thus, rotation of the coil tubing within the production column drives the rotor of the rotary pump.
Thus, there remains a need in the industry for a downhole production system and method which address the disadvantages associated with the conventional use of a rod string to actuate a downhole pump.
The present invention relates to an apparatus and a method for use in pumping fluids in a wellbore. Further, the apparatus and method are preferably for use with a downhole rotary pump. More particularly, a pipe string defining an interior fluid path for the passage of the fluids therein actuates the downhole rotary pump in order to pump the fluids. Preferably, the pipe string is comprised of a tubing string rotatably supported within the wellbore. Thus, the pipe string preferably performs the dual function of providing a fluid path for the passage of the fluids and actuating the downhole rotary pump.
Although the apparatus and the method may be used for injecting fluids in the wellbore from the surface downhole to a desired underground formation, the apparatus and method are preferably used for producing fluids in the wellbore from the underground formation to the surface. Further, the apparatus and the method may be used for pumping any fluids, which fluid may be comprised of any liquids, gases or a combination thereof. However, the fluid is preferably comprised of a hydrocarbon, such that the apparatus and the method are preferably used for pumping production fluids from an underground hydrocarbon producing formation. The fluid may also contain an amount of solid material such as sand or debris from the wellbore.
In a first aspect of the invention, the invention is comprised of an apparatus for use in pumping fluids in a wellbore. The apparatus comprises:
(a) a pipe string positioned in the wellbore and extending between a wellhead end of the pipe string and a production end of the pipe string, the pipe string defining an interior fluid path from the wellhead end to the production end;
(b) a swivel device connected into the pipe string between the wellhead end and the production end so that an upper portion of the pipe string between the wellhead end and the swivel device may rotate relative to a lower portion of the pipe string between the swivel device and the production end;
(c) a lower connector for connecting the lower portion of the pipe string with a stator of a rotary pump positioned at the production end of the pipe string such that a fluid which is pumped by the pump is conducted through the interior fluid path of the pipe string; and
(d) an upper connector for connecting the upper portion of the pipe string with a rotor of the rotary pump such that rotation of the upper portion of the pipe string will result in rotation of the rotor and in pumping of the fluid by the pump.
In a second aspect of the invention, the invention is comprised of a method for pumping fluids from a wellbore. The method is comprised of the following steps:
(a) rotatably supporting an upper portion of a pipe string in a wellbore at a wellhead end of the pipe string;
(b) connecting a lower portion of the pipe string with a stator of a rotary pump at a production end of the pipe string, wherein the upper portion of the pipe string and the lower portion of the pipe string are capable of rotating relative to each other;
(c) connecting the upper portion of the pipe string with a rotor of the rotary pump;
(d) positioning the pump in the wellbore; and
(e) rotating the upper portion of the pipe string in order to rotate the rotor of the rotary pump to pump a fluid and in order to conduct the fluid through an interior fluid path in the pipe string.
The method of the within invention may be performed by any apparatus suitable for, and capable of, performing the method. However, preferably, the apparatus of the within invention is used to perform the method. More preferably, the preferred embodiment of the apparatus, as described herein, is used to perform the method.
In the first aspect of the invention, the swivel device may be comprised of any apparatus, structure or mechanism which may be connected into the pipe string and which provides for or permits the rotation of the upper portion of the pipe string relative to the lower portion of the pipe string. Further, the swivel device may be connected into the pipe string in any manner and by any mechanism, structure or method. For instance, the swivel device may be integrally formed with the upper portion and the lower portion of the pipe string. Alternately, the swivel device may be fixedly connected with the pipe string, such as by welding, or it may be removably coupled or attached with the pipe string, such as by a threaded coupling or sub.
However, the swivel device is preferably comprised of a housing for containing a lower end of the upper portion of the pipe string and for containing an upper end of the lower portion of the pipe string. Further, the housing is preferably comprised of an upper housing support for engaging the upper portion of the pipe string and a lower housing support for engaging the lower portion of the pipe string, wherein the lower portion of the pipe string and the upper portion of the pipe string are rotatably supported relative to each other by the upper housing support and the lower housing support.
At least one of the upper housing support and the lower housing support preferably permit rotation of the housing relative to the pipe string. For instance, the upper housing support may permit rotation of the housing relative to the pipe string. Thus, the upper portion of the pipe string will be permitted to rotate relative to the housing, which preferably remains substantially stationary. Alternatively, the lower housing support may permit rotation of the housing relative to the pipe string. Thus, the upper portion of the pipe string and the housing will be permitted to rotate together as a unit relative to the lower portion of the pipe string, which preferably remains substantially stationary.
In the preferred embodiment, both the upper housing support and the lower housing support permit rotation of the housing relative to the pipe string. Thus, in the event that one of the upper or lower housing supports fails or otherwise does not permit rotation of the housing relative to the portion of the pipe string contained therein, then the other housing support will continue to permit such relative rotation and the continued functioning of the swivel device. In this manner, the useful life of the swivel device may be extended.
The upper and lower housing supports may be each comprised of any structure, mechanism or device able to engage and support the adjacent upper and lower portions of the pipe string respectively. Further, at least one, and preferably both, of the upper and lower housing supports is comprised of a structure, mechanism or device able to rotatably support the upper and lower portions of the pipe string respectively such that the housing is permitted to rotate relative to the portion of the pipe string contained therein.
Preferably, the upper housing support supports the upper portion of the pipe string both radially and axially. Similarly, the lower housing support preferably supports the lower portion of the pipe string both radially and axially. Thus, in the preferred embodiment, at least one, and preferably both, of the upper and lower housing supports is comprised of at least one thrust bearing for supporting the pipe string axially and at least radial bearing for supporting the pipe string radially.
Further, the swivel device is preferably comprised of an upper seal assembly for sealing between the upper portion of the pipe string and the housing and a lower seal assembly for sealing between the lower portion of the pipe string and the housing. Each seal assembly may be comprised of one or more seals, sealing devices or other suitable sealing structures able to provide the desired sealing between the pipe string and the housing.
The upper connector of the apparatus may be comprised of any apparatus, structure or mechanism capable of connecting the upper portion of the pipe string with the rotor of the rotary pump such that rotation of the upper portion of the pipe string will result in rotation of the rotor. For instance, the upper connector may be integrally formed into or with one or both of the upper portion of the pipe string and the rotor of the rotary pump. Alternately, the upper connector may be fixedly connected into or with one or both of the upper portion of the pipe string and the rotor, such as by welding, or it may be removably coupled or attached into or with one or both of the upper portion of the pipe string and the rotor, such as by a threaded coupling or connection.
However, preferably, the upper connector is comprised of a drive sub collar which is connected into the upper portion of the pipe string such that rotation of the upper portion of the pipe string will result in rotation of the drive sub collar. The drive sub collar may be connected, coupled or otherwise mounted into the upper portion of the pipe string by any structure, mechanism or device able to provide the necessary connection. For instance, as indicated above, the drive sub collar may be integrally formed into the pipe string, fixedly connected into the pipe string such as by welding, removably connected into the pipe string such as by a threaded connection or a combination thereof.
Further, the drive sub collar is preferably comprised of a rotor connector for connecting the rotor of the pump to the drive sub collar such that rotation of the upper portion of the pipe string and the drive sub collar will result in rotation of the rotor. The rotor connector may be comprised of any apparatus, structure or mechanism capable of connecting the rotor of the rotary pump to the drive sub collar. In addition, the rotor connector may be integrally formed with one or both of the drive sub collar and the rotor of the rotary pump. Alternately, the rotor connector may be fixedly connected or mounted with one or both of the drive sub collar and the rotor, such as by welding, or it may be removably coupled or attached with one or both of the drive sub collar and the rotor, such as by a threaded coupling or connection.
As well, in the preferred embodiment, the rotor connector is located concentrically within the drive sub collar so that the drive sub collar and the rotor connector are rotatable about a common axis.
Further, the drive sub collar is preferably comprised of an upper end and a lower end. In addition, the drive sub collar preferably defines an interior fluid passage for permitting fluid to be conducted between the upper end and the lower end of the drive sub collar. In the preferred embodiment, the interior fluid passage defined by the drive sub collar is comprised of a plurality of fluid channels surrounding the rotor connector. Thus, the drive sub collar does not significantly interfere with or impede the passage of fluids through the interior fluid path defined by the pipe string.
The lower connector of the apparatus may be comprised of any apparatus, structure or mechanism capable of connecting the lower portion of the pipe string with the stator of the rotary pump such that fluid pumped by the rotary pump is conducted through the interior fluid path of the pipe string. For instance, the lower connector may be integrally formed into or with one or both of the lower portion of the pipe string and the stator of the rotary pump. However, alternately, the lower connector may be fixedly connected into or with one or both of the lower portion of the pipe string and the stator, such as by welding, or it may be removably coupled or attached into or with one or both of the lower portion of the pipe string and the stator, such as by a threaded coupling or connection.
Preferably, the lower connector is comprised of a sub or collar which is connected into or with the lower portion of the pipe string, preferably between the production end of the pipe string and the stator of the rotary pump positioned at the production end. The collar may be connected, coupled or otherwise mounted between the lower portion of the pipe string at the production end and the stator by any structure, mechanism or device able to provide the necessary connection. In the preferred embodiment, the collar is integrally formed with one or both of the lower portion of the pipe string and the stator, preferably with the lower portion. However, alternately, the collar may be fixedly connected with one or both of the lower portion of the pipe string and the stator such as by welding, removably connected with one or both of the lower portion of the pipe string and the stator such as by a threaded connection or a combination thereof.
Further, the pipe string is comprised of an exterior surface. Preferably, the apparatus is further comprised of at least one stabilizing collar mounted on the exterior surface of the upper portion of the pipe string for centralizing the pipe string in the wellbore. More preferably, the apparatus is comprised of a plurality of stabilizing collars spaced longitudinally along the upper portion of the pipe string.
The stabilizing collar may be comprised of any structure, mechanism or device capable of centralizing the upper portion of the pipe string within the wellbore, particularly upon the rotation of the upper portion in the wellbore. Further, the stabilizing collar may be fixedly mounted with the exterior surface by any mechanism, structure or device capable of fixedly mounting, connecting or affixing the stabilizing collar thereto such that the stabilizing collar rotates with the upper portion of the pipe string.
However, preferably, the stabilizing collar is rotatably mounted on the exterior surface of the upper portion of the pipe string. Thus, the upper portion of the pipe string is rotatable within, or relative to, the stabilizing collar. In this case, the stabilizing collar may be rotatably mounted with the exterior surface by any mechanism, structure or device capable of rotatably mounting, connecting or affixing the stabilizing collar thereto such that the upper portion of the pipe string is permitted to rotate relative to the stabilizing collar.
In the preferred embodiment, the stabilizing collar is comprised of an inner surface for surrounding the exterior surface of the pipe string. Further, the stabilizing collar is comprised of an outer sleeve for contacting an inner wellbore surface. The outer sleeve is preferably comprised of a material which will not abrade substantially the inner wellbore surface. Although any non-abrading material may be used, in the preferred embodiment, the outer sleeve of the stabilizing collar is comprised of a polyurethane.
The apparatus may be further comprised of a wellhead support located at the wellhead end of the pipe string for supporting the pipe string in the wellbore. Preferably, the wellhead support rotatably supports the pipe string in the wellbore.
Finally, the apparatus is preferably further comprised of a drive system connected with the upper portion of the pipe string for rotating the upper portion of the pipe string. Accordingly, actuation of the drive system actuates the rotary pump. Specifically, actuation of the drive system rotates the upper portion of the pipe string connected with the rotor of the rotary pump and thereby results in rotation of the rotor and pumping of the fluid by the rotary pump.
The drive system may be connected with the upper portion of the pipe string at any location or position longitudinally along the length of the pipe string between the wellhead end of the pipe string and the lower end of the upper portion of the pipe string. However, preferably, the drive system is connected with the upper portion of the pipe string at, adjacent or in proximity to the wellhead end of the pipe string.
In the second aspect of the invention, the step of rotatably supporting the upper portion of the pipe string may be performed in any manner and using any method, structure, mechanism or device capable of rotatably supporting the upper portion in the wellbore at, adjacent or in proximity to the wellhead end of the pipe string. However, the rotatably supporting step is preferably performed by providing the wellhead support, described above for the apparatus embodiment of the invention, at the wellhead end of the pipe string. Further, the rotatably supporting step is preferably comprised of mounting, connecting, coupling or otherwise associating the upper portion of the pipe string with the wellhead support at, adjacent or in proximity to the wellhead end of the pipe string in a manner such that the pipe string is rotatably supported within the wellbore by the wellhead support.
Further, the step of connecting the lower portion of the pipe string with the stator may be performed in any manner and using any method, structure, mechanism or device capable of connecting the lower portion and the stator such that the fluid pumped by the pump may be conducted through the interior fluid path of the pipe string. However, the lower portion connecting step is preferably performed by providing the lower connector, described above for the apparatus embodiment of the invention, for connecting the lower portion of the pipe string with the stator. Further, the lower portion connecting step is preferably comprised of mounting, connecting, coupling or otherwise associating the lower portion at the production end of the pipe string and the stator with the lower connector in a manner such that the fluid may be conducted between the pump and the interior fluid path of the pipe string.
The step of connecting the upper portion of the pipe string with the rotor may be performed in any manner and using any method, structure, mechanism or device capable of connecting the upper portion and the rotor such that rotation of the upper portion results in rotation of the rotor. However, the upper portion connecting step is preferably performed by providing the upper connector, described above for the apparatus embodiment of the invention, for connecting the upper portion of the pipe string with the rotor. Further, the upper portion connecting step is preferably comprised of mounting, connecting, coupling or otherwise associating the upper portion of the pipe string and the rotor with the upper connector in a manner such that rotation of the upper portion results in rotation of the rotor and thus, pumping of the fluid.
The rotating step may be performed in any manner and using any method, structure, mechanism or device capable of rotating the upper portion of the pipe string in the wellbore. However, the rotating step is preferably performed by providing the drive system, described above for the apparatus embodiment of the invention. Further, the rotating step is preferably comprised of mounting, connecting, coupling or otherwise associating the upper portion of the pipe string with the drive system, preferably at, adjacent or in proximity to the wellhead end of the pipe string.
The positioning step may be performed in any manner and using any method, structure, mechanism or device capable of positioning the pump in the wellbore. The positioning step may be performed prior to one or both of the upper portion connecting step and the lower portion connecting step. Thus, the pump may be positioned in the wellbore before being connected with the pipe string, or with either or both of the upper and lower portions of the pipe string. However, the positioning step is preferably performed following the upper portion connecting step and the lower portion connecting step. Thus, preferably, the pump is positioned in the wellbore after being connected with the pipe string. In other words, the pump is preferably positioned in the wellbore after being connected with both the upper portion and the lower portion of the pipe string.
Finally, the method of the within invention may be further comprised of the step of anchoring the stator in the wellbore during rotation of the upper portion of the pipe string in order to inhibit rotation of the stator. The anchoring step may be performed in any manner and using any method, structure, mechanism or device capable of anchoring the stator in the wellbore. However, the anchoring step is preferably performed by mounting, connecting, coupling or otherwise associating an anchor or anchoring device, such as a torque anchor, with the stator of the rotary pump.